Droidicon Emperor

The Drodican Emperor is the ruler of the Droidican race. He is found only in The Imperial Palace. Little is known about him other than that printed in the manual:

The Drodican Emperor is a poisonous foe. You'll have to face him on his home turf: the Royal Chambers, which is a strange and unnerving place. The Emperor runs from one side of the chamber to the other, alternately throwing poison at you and then releasing a robot to help him in his attack. Shoot the robot and avoid the Emperor's poison.

As one of the three bosses in Keen GBC, when you defeat the Emperor you will receive a Plasma Crystal.

There is a switch on the lower left side. Stand on it and press the Select button while the Emperor is in the middle of the screen. Shooting him does not work.